We prefer to price our projects on a fixed-price basis. This way, once we’ve set up the commercial basis of the project we can turn our attention wholly to its implementation. We can accommodate reasonable changes to your business requirements as the project progresses, without having to watch the clock all the time.
This approach depends crucially upon a trusting relationship between the two of us: we trust you to go easy on the change requests, and you trust us to build a system that is truly useful to you. We like doing business that way.